This application claims the priority of German Patent Application, Serial No. 101 44 992.5, filed Sep. 12, 2001, pursuant to 35 U.S.C. 119(a)-(d), the subject matter of which is incorporated herein by reference.
The present invention relates to a mold mounting plate of an injection molding machine.
U.S. Pat. No. 5,593,711 discloses a mold mounting plate for a plastic injection molding machine which consists essentially of a backplate, a center section formed as a half-pipe or a frustrated cone, and a baseplate extending parallel to the backplate for receiving the mold. The backplate has in its corner regions openings for receiving four columns of an injection molding machine. The center section, which is formed as a hollow body, it is arranged with its base in the center of the backplate. The baseplate for the mold is located adjacent to the tip of the frustrated cone or the half-pipe. The baseplate is hence supported by the center part only in its center region.
The aforedescribed mold mounting plate is intended to reduce the weight of the plate and the deformation of the plate under the pressing force during the injection molding process, thereby preventing the mold halves from opening. However, a finite element analysis has shown that such mold mounting plates which are formed as so-called trusses, i.e., which introduce the load like a roof ridge diagonally to a base, are disadvantageous for static reasons.
The same U.S. patent describes in the background section another mold mounting plate for an injection molding machine, which essentially consists of two plates, namely a baseplate and a backplate. The baseplate is here connected by a rib-like structure with a backplate that is parallel to the baseplate. The backplate has a smaller surface area than the baseplate, so that the mold mounting plate has a slightly roof-shaped cross-section. The rectangular mold mounting plate has at each of its corner an opening for receiving the columns of an injection molding machine. The rib-like structure of the mold mounting plate which is essentially formed of a plurality of ribs and slots, is primarily intended to support the weight of the mold mounting plate.
Since the baseplate of the mold mounting plate is under pressure during the injection molding process, the rib-like structure causes the backplate to be under tension. Accordingly, the mold mounting plate yields so that the columns located in the openings are displaced inwardly on the side of the baseplate and are subjected to a bending stress.
It would therefore be desirable to provide to a stable mold mounting plate for an injection molding machine which obviates prior art shortcomings and is simple in structure and is easy to manufacture.
According to one aspect of the present invention, a mold mounting plate of an injection molding machine, in particular for plastic injection molding, includes a baseplate with a front side for receiving a mold and a dome-shaped element having a base that is arranged on the backside of the baseplate opposite the front side to support the baseplate. In this way, a particularly light and rigid construction is achieved. Such a mold mounting plate minimizes torque transmission to the column-like holding and/or guide elements of an injection molding machine as a result of the deformation of the mold mounting plate.
Advantageous embodiments may include one or more of the following features. The dome-shaped element can be symmetric and arranged centrally on the backside of the baseplate. To facilitate receiving an injection unit of the plastic injection molding machine, the dome-shaped element has a recess disposed in the region of its apex wherein the recess extends in the direction of the baseplate all to way to the baseplate. The dome-shaped element has a tapered section in the direction of the baseplate, with the tapered section being symmetric to the center of the baseplate. The ring-shaped tapered section promotes a stable support of the center of the baseplate in spite of the opening provided for the injection unit. The substantially narrow shape of the tapered section and the massive size of the dome-shaped element in the region of the tapered section support the foundation of the baseplate. In this way, the pressing forces can be transmitted directly from the baseplate to the dome-shaped element.
For reducing the weight, the dome-shaped element can include ribs with recesses formed in the marginal region of the baseplate, wherein the ribs can be oriented outwardly and parallel to the edges of the baseplate. In addition, in the region of the recesses, the wall of the dome-shaped element can be arranged perpendicular to the baseplate and window-shaped openings can be arranged in the wall of the dome-shaped element in the region of the recesses as well as between the ribs. The ribs can also be arranged perpendicular to the baseplate in the region of the recesses.
Openings can also be provided in the baseplate for receiving columnar holding and/or guide elements of an injection molding machine. The openings can be arranged outside the dome-shaped element, and sleeves, which can be shaped as parallelepipeds, can be disposed adjacent to the openings for receiving to the columnar holding and/or guide elements. The sleeves are thus elastically connected to the baseplate and can bend, providing some compensation in the alignment. The baseplate is preferably four-sided, with an opening disposed in each corner region.
To provide sufficient rigidity of the baseplate for longer mold mounting plates also in the region of the marginal edges, two space-apart ribs are arranged between each of the sleeves.
The weight can be further reduced by disposing a cavity, which is separated by an intermediate wall extending through the center of and perpendicular to the baseplate, between the dome-shaped element and the baseplate. Preferably, the intermediate wall extends parallel to the marginal edge of the four-sided baseplate and, for a rectangular baseplate, parallel to the shorter marginal edge of the baseplate. This increases in the stability of the baseplate, thereby providing sufficient rigidity also for longer mold mounting plates. In addition, the mold mounting plate can be cast with only two lost cores, which is more economical.
For static considerations, the dome-shaped element can advantageously transition into the sleeves in the corner regions of the baseplate, wherein the sleeves can have a smaller height that the maximum height of the dome-shaped element as measured relative to the baseplate. The radius of the dome-shaped element can correspond approximately to the spacing between the axes of the columnar holding and/or guide elements. Advantageously, the baseplate, the dome-shaped element, the sleeves, and the ribs are formed as a single cast part.